I think it's to do with the kind of sensors each camera uses. I believe that prior to Live View and the latest generations, DSLR sensors needed a physical shutter to precisely control the amount of light hitting them - and as Canon's silent shoot implementation shows, there's still a physical process in there.

Whereas P&S sensors could be effectively 'switched on and off' to deliver the required exposure time, while also being able to deliver a live video feed for composition.

I think Thomas may have a point, from what i see, P&S are trying to mimic the SLR or DSLR by adding in the 'shutter' sound though there is none.
The shutter sound was and is considered 'necessary'
I remembered the earlier P&S does not produced any sound and was not well received and later the sound of the 'shutter' was added.

Same for the camera-phone, they all have 'shutter' sound now.

Perhaps in the near-future the shutter will be deemed 'irrelevant' or not required

I assume Thomas was asking why a DSLR technically needed a physical shutter, but that's also a great point about P&S and phone manufacturers including a shutter sound!

I think it's a familiar sound which people know and recognise, and it also serves to tell you the photo's been taken. It would be funny though if a physical shutter is eventually unneccessary on future DSLRs and they also play back a recording!

Hi antman! I'm not talking about the mirror, but the extra shutter behind the mirror.
And P&S make nice 30fps movies too, so I really, really don't get the function of the shutter:
- it's loud
- it's prone to malfunction/wear&tear
- it increases the costs
So why not put away with it?

Yup, I was astonished as you, when I understood that there is a real shutter just like in film-SLRs in front of the sensor. You can see it in some of the Nikon D3/00 detail shots, just don't have a link handy...

The pic above is definitely wrong with regard to most current DSLRs. (btw. if you google "nikon d300 shutter.jpg", you'll find a pic of the shutter). But perhaps the schematic was simplifying with respect to sensor+shutter, as it was focussing - err - on the focussing system...

For the D300 I can quote: "shutter: Electronically-controlled vertical-travel focal plane shutter" and for the D3 they talk of "Nikon's Self-diagnostic shutter system, tested to 300,000 cycles, is a clear indication of advanced engineering and durable construction".

Hi Guys, all current DSLRs have physical shutters in front of the sensors in exactly the same way as older 35mm models had shutters in front of the film itself. The mirror is the part of the optical SLR design which redirects light from the lens through the viewfinder.

The mirror can't flip up and back again quickly enough or have its timings adjusted accurately to act as a shutter though. This explains why there's a need for a physical shutter on a film camera. But the question is why you can't flip the mirror up, then just switch the sensor on and off to eliminate the need for a shutter in a DSLR - and its noise.

I think it's due to the way DSLR sensors are designed, although this could change in the future...